What If You Only Sometimes Work Out?

Here’s what intermittent exercise does to the body

Illustration: Luyi Wang

It’s pretty common to have an on-again, off-again relationship with exercise. But isn’t working out sometimes better than not working out at all?

Mostly, yes.

New thinking from exercise scientists suggests that occasional exercise still benefits the body, even if it’s inconsistent. Studies from the last few years have shown that people who cram their weekly exercise into one or two days on the weekend — so-called “weekend warriors” — can make up for a week of sloth. “If you choose to exercise only on the weekends and equal the volume of someone exercising three days a week during the week, you get the same health benefits,” says Linda Pescatello, PhD, a kinesiology professor at the University of Connecticut.

The body changes quickly with exercise. Within weeks, cardiovascular endurance and flexibility improve and activity feels easier as the body becomes more efficient at breathing and regulating oxygen, says Melissa Morris, a certified exercise physiologist and educator. “Individuals may also notice some fat loss and muscle gain within four to six weeks,” she says, along with lower blood pressure, better mental health, and more energy. These improvements continually increase as people remain active, though they may…